Ethylbenzene from benzene and ethylene

If the byproduct reaction is reversible and inerts are present, then changing the concentration of inerts if there is a change in the number of moles should be considered, as discussed above. Whether or not there is a change in the number of moles, recycling byproducts can suppress their formation if the bj iroduct-forming reaction is reversible. An example is in the production of ethylbenzene from benzene and ethylene ... 

Among the wide variety of organic reactions in which zeolites have been employed as catalysts, may be emphasized the transformations of aromatic hydrocarbons of importance in petrochemistry, and in the synthesis of intermediates for pharmaceutical or fragrance products.5 In particular, Friede 1-Crafts acylation and alkylation over zeolites have been widely used for the synthesis of fine chemicals.6 Insights into the mechanism of aromatic acylation over zeolites have been disclosed.7 The production of ethylbenzene from benzene and ethylene, catalyzed by HZSM-5 zeolite and developed by the Mobil-Badger Company, was the first commercialized industrial process for aromatic alkylation over zeolites.8 Other typical examples of zeolite-mediated Friedel-Crafts reactions are the regioselective formation of p-xylene by alkylation of toluene with methanol over HZSM-5,9 or the regioselective p-acylation of toluene with acetic anhydride over HBEA zeolites.10 In both transformations, the p-isomers are obtained in nearly quantitative yield. 

We have seen previously shape-selective catalysis by ZSM-5 in the conversion of methanol to gasoline (Chapter 15).-7 Other commercial processes include the formation of ethylbenzene from benzene and ethylene and the synthesis of p-xylene. The efficient performance of ZSM-5 catalyst has been attributed to its high acidity and to the peculiar shape, arrangement, and dimensions of the channels. Most of the active sites are within the channel so a branched chain molecule may not be able to diffuse in, and therefore does not react, while a linear one may do so. Of course, once a reactant is in the channel a cavity large enough to house the activated complex must exist or product cannot form. Finally, the product must be able to diffuse out. and in some instances product size and shape exclude this possibility. For example, in the methylu-uon of toluene to form xylene ... 

TYPICAL OPERATING DATA ETHYLBENZENE FROM BENZENE AND ETHYLENE... 

In a substitution, a molecular fragment of a reactant is replaced by a fragment of another reactant. A prominent example is the alkylation where an alkyl group is transferred from one molecule to another. E.g., the production of Ethylbenzene from Benzene and Ethylene by the so-called Priedel-Crafts alkylation is a standard process in chemical industry. " ... 

Since it is basically more economical to synthesize ethylbenzene from benzene and ethylene (see Chapter 5.1.2), distillation is used only in isolated cases, particularly in the USA (Cosden),... 

The synthesis of ethylbenzene from benzene and ethylene was discovered in 1879 by M.Balsohn, who introduced ethylene gas into a mixture of benzene and aluminum chloride, and with heating to 70 to 80 °C obtained ethylbenzene and higher alkylated benzenes. In 1891, ethylbenzene was found in the xylene fraction of coal tar. 

Improvements in chemical processes are very often based on the discovery or development of new catalysts or adsorbents. One particularly exciting example in the field of zeolite catalysis is the replacement of the formerly used amorphous silica-aliunina catalysts in fluid catalytic cracking (FCC) of vacuiun gas oil by rare earth exchanged X-type zeoUtes [1]. This resulted in considerably improved yields of the desired gasoUne and, hence, a much more efficient utilization of the crude oil. Fiuther examples are the introduction of zeolite HZSM-5 as catalyst in the synthesis of ethylbenzene from benzene and ethylene [2], for xylene isomerization [3] and for the conversion of methanol to high-... 

Figure 3.6 Production of ethylbenzene from benzene and ethylene...

Alkenyl halides such as vinyl chloride (H2C=CHC1) do not form carbocations on treatment with aluminum chloride and so cannot be used m Friedel-Crafts reactions Thus the industrial preparation of styrene from benzene and ethylene does not involve vinyl chloride but proceeds by way of ethylbenzene... 

Alkylation. Ethylbenzene [100-41 -4] the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either ia the Hquid phase ia the preseace of a Eriedel-Crafts catalyst (AlCl, BE, EeCl ) or ia the vapor phase with a suitable catalyst. The Moasanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeoHte catalyst process for Hquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process usiag zeoHte catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-5] which is obtained by dehydrogenation ia the preseace of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

Ethylbenzene is made from benzene and ethylene in the gas phase at 260°C and 40 atm. 

The generation of caibocations from these sources is well documented (see Section 5.4). The reaction of aromatics with alkenes in the presence of Lewis acid catalysts is the basis for the industrial production of many alkylated aromatic compounds. Styrene, for example, is prepared by dehydrogenation of ethylbenzene made from benzene and ethylene. 

Ethylbenzene has not been separated commercially from Cg aromatics because it cannot be obtained therefrom in high purity as readily as it can be synthesized from benzene and ethylene by alkylation to provide the necessary stock for styrene manufacture. The current shortage of benzene, however, re-establishes interest in separating ethylbenzene from hydroformed stocks. 

Ethylbenzene (boiling point 136°C, density 0.8672, flash point 21°C) is a colorless liquid that is manufactured from benzene and ethylene by several modifications of the older mixed liquid-gas reaction system using aluminum chloride as a catalyst (Friedel-Crafts reaction). The reaction takes place in the gas phase over a fixed-bed unit at 370 C under a pressure of 1450 to 2850 kPa. Unchanged andpolyethylated materials are recirculated, making a yield of 98 percent possible. The catalyst operates several days before requiring regeneration. 

Application Production of polymer-grade styrene monomer (SM) from benzene and ethylene. The Lummus/UOP EBOne process is used to alkylate benzene with ethylene to form ethylbenzene (EB). The EB is then dehydrogenated to SM using the Lummus/UOP Classic SM process. 

Styrene is one of the most important substances as a raw material of polymers. In Japan, 1.5 million tons of styrene is produced every year. It is commercially produced by the dehydrogenation of ethylbenzene (equation 1), which is made from benzene and ethylene (equation 2). 

Thus, the industrial preparation of styrene from benzene and ethylene does not involve vinyl chloride but proceeds by way of ethylbenzene. 

The following alkylated benzenes are of major industrial importance ethylbenzene produced from benzene and ethylene cumene from benzene and propylene and dodecylbenzenes from benzene and linear C12 olefins. Both liquid catalysts and more recently solid catalysts are employed commercially. 

Shown below is a portion of a process that produces styrene from benzene and ethylene (see Exercise 2.12). Benzene is recycled to an alkylation reactor and the by-product ethylbenzene is recycled to a dehydrogenation reactor. Stream 2 is 28.0% of stream 1. Also, 97.0% of the ethylbenzene in stream 3 leaves distillation column 2 via stream 4. Calculate the flow rate and composition of stream 5. 

Ethylbenzene is the key intermediate in the manufacture of styrene, one of the most important industrial monomers. Almost all ethylbenzene is synthesized from benzene and ethylene. 

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